Abstract

Background and Aims: Studies have suggested that smokers may have a higher risk of primary biliary cholangitis (PBC) although the results have been inconsistent. This systematic review and meta-analysis aim to better characterize the risk of PBC among smokers by identifying all relevant studies and summarizing their results together.
Methods: A comprehensive literature review was conducted using Embase and Pubmed/MEDLINE databases from inception to September 2018 to identify all studies which compared the risk of PBC among current, ever and former smokers to non-smokers. Effect estimates from each study were extracted and combined together using the random-effect, generic inverse variance method of DerSimonian and Laird.
Results: Nine case-control studies with 21,577 participants met the eligibility criteria and were included in the meta-analysis. The risk of PBC among ever smokers was significantly higher than non-smokers with the pooled odds ratio (OR) of 1.31 (95% CI, 1.03-1.67; I 2 89%). Subgroup analysis found that the risk was higher in both former smokers (pooled OR 1.36; 95% CI, 1.01-1.84; I 2 75%) and current smokers (pooled OR 1.18; 95% CI, 0.94-1.50; I 2 79%), although the latter did not reach statistical significance. Immunomodulatory and cytotoxic effect of cigarettes were the possible mechanisms behind this increased risk.
Conclusions: A significantly increased risk of PBC among individuals who ever smoked was observed in this study, adding to the already long list of harmful health consequences of smoking.

Keywords

primary biliary cholangitis, biliary cirrhosis, smoking, cigarettes, meta-analysis